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Haldol Decanoate Side Effects

Generic Name: haloperidol

Note: This page contains information about the side effects of haloperidol. Some of the dosage forms included on this document may not apply to the brand name Haldol Decanoate.

In Summary

More frequent side effects include: constipation, weight gain, blurred vision, menstrual disease, myasthenia, lactation, akathisia, shuffling gait, dysphagia, mask-like face, dysphasia, restlessness, xerostomia, and mastalgia. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to haloperidol: oral solution, oral tablet

In addition to its needed effects, some unwanted effects may be caused by haloperidol (the active ingredient contained in Haldol Decanoate). In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking haloperidol:

More common:
  • Difficulty with speaking or swallowing
  • inability to move the eyes
  • loss of balance control
  • mask-like face
  • muscle spasms, especially of the neck and back
  • restlessness or need to keep moving (severe)
  • shuffling walk
  • stiffness of the arms and legs
  • trembling and shaking of the fingers and hands
  • twisting movements of the body
  • weakness of the arms and legs
Less common:
  • Decreased thirst
  • difficulty in urination
  • dizziness, lightheadedness, or fainting
  • hallucinations (seeing or hearing things that are not there)
  • lip smacking or puckering
  • puffing of the cheeks
  • rapid or worm-like movements of the tongue
  • skin rash
  • uncontrolled chewing movements
  • uncontrolled movements of the arms and legs
  • Confusion
  • convulsions (seizures)
  • difficult or fast breathing
  • fast heartbeat or irregular pulse
  • fever (high)
  • high or low blood pressure
  • hot, dry skin, or lack of sweating
  • increased blinking or spasms of the eyelid
  • increased sweating
  • loss of bladder control
  • muscle stiffness (severe)
  • muscle weakness
  • sore throat and fever
  • uncontrolled twisting movements of the neck, trunk, arms, or legs
  • unusual bleeding or bruising
  • unusual facial expressions or body positions
  • unusual tiredness or weakness
  • unusually pale skin
  • yellow eyes or skin
Incidence not known:
  • Continuing nausea or vomiting
  • increase in the frequency of seizures
  • loss of appetite
  • swelling of the face
  • tiredness and weakness

If any of the following symptoms of overdose occur while taking haloperidol, get emergency help immediately:

Symptoms of overdose:
  • Difficulty with breathing (severe)
  • dizziness (severe)
  • drowsiness (severe)
  • muscle trembling, jerking, stiffness, or uncontrolled movements (severe)
  • unusual tiredness or weakness (severe)

Minor Side Effects

Some of the side effects that can occur with haloperidol may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:
  • Blurred vision
  • changes in menstrual period
  • constipation
  • dryness of the mouth
  • swelling or pain in the breasts (in females)
  • unusual secretion of milk
  • weight gain
Less common:
  • Decreased sexual ability
  • drowsiness
  • increased sensitivity of the skin to sun (skin rash, itching, redness or other discoloration of skin, or severe sunburn)
  • nausea or vomiting

For Healthcare Professionals

Applies to haloperidol: compounding powder, injectable solution, intramuscular solution, oral concentrate, oral tablet


Local side effects have included noninfectious, edematous, pruritic, tender masses after intramuscular injection of haloperidol (the active ingredient contained in Haldol Decanoate) decanoate. These resolved slowly over months.[Ref]

Nervous system

The drowsiness associated with haloperidol (the active ingredient contained in Haldol Decanoate) therapy may resolve after several doses.

Tardive dyskinesia involves involuntary, dyskinetic, repetitive movements and may be more common in elderly women receiving haloperidol. Tardive dyskinesia may be irreversible and is related to both the duration of therapy and the total amount of drug consumed. Frequent discontinuation and resumption of therapy may predispose patients to the development of tardive dyskinesia.

A study of 19 Veteran Administration hospital patients receiving haloperidol decanoate has reported a prevalence rate for tardive dyskinesia of 42%.

Dystonias frequently involve tongue protrusions, muscle rigidity, torticollis, and opisthotonos. Dystonias usually resolve after neuroleptic discontinuation, but may require antihistamine and antiparkinsonian therapy if symptoms are severe or if respiration is compromised. Treatment of dystonic reactions and extrapyramidal effects, in addition to general supportive measures, may include judicious use of one or more of the following: benztropine, trihexyphenidyl, biperiden or diphenhydramine.

Pseudo-parkinsonism involves flat facies, pill-rolling tremor, shuffling gait, and cogwheel rigidity. Pseudo-parkinsonian symptoms may respond to judicious use of one or more of the following: benztropine, trihexyphenidyl, biperiden or diphenhydramine.

Fever, altered consciousness, autonomic dysfunction and muscle rigidity are the hallmarks of the neuroleptic malignant syndrome. The neuroleptic malignant syndrome is associated with a case fatality rate of about 20%. Immediate discontinuation of neuroleptic therapy, consideration of dantrolene administration as well as intensive monitoring and supportive care are indicated.

Seizures associated with haloperidol have been reported, but many of the reports involved patients with a history of seizures or underlying organic brain disease.

Lower (worse) baseline scores predicted greater cognitive improvement. Change In cognitive performance was weakly related to change in symptom scores.[Ref]

Nervous system side effects are common and have included sedation, drowsiness, and rarely seizures. Tardive dyskinesia, dystonia, pseudo-parkinsonism, increased neuromuscular excitability, and the neuroleptic malignant syndrome (NMS) have also been reported. Low doses of haloperidol have been associated with improvement on cognitive test performance in patients in the early stages of schizophrenia.[Ref]


Other side effects including the anticholinergic effects constipation, dry mouth, urinary retention, and blurred vision have been reported.[Ref]


Baseline and periodic monitoring of liver function tests during haloperidol (the active ingredient contained in Haldol Decanoate) therapy is recommended for patients with liver disease.[Ref]

Hepatic side effects including transient elevations in liver function tests have been reported.[Ref]


Cardiovascular side effects including hypotension, hypertension, tachycardia, and cardiac arrest associated with haloperidol (the active ingredient contained in Haldol Decanoate) therapy have been reported rarely (although many of these patients have had serious underlying diseases). A number of cases of prolonged QT interval and torsades de pointes have been reported in patients treated with parenteral haloperidol. Sudden death and unexpected death have also been associated with haloperidol administration.[Ref]

Most of the cases of prolonged QT interval and torsades de pointes have involved patients treated for intensive care unit delirium. Cardiac monitoring is recommended for intensive care unit patients who must receive haloperidol for delirium.[Ref]


Endocrinologic side effects including hyperprolactinemia and galactorrhea have been reported. Haloperidol-induced hyperprolactinemia has been associated with sexual dysfunction in some male patients.[Ref]

One in vitro study has suggested that haloperidol may increase sperm motility.

According to one report involving patients on long-term haloperidol use (mean dose 15.7 mg/day; mean duration of illness 15.5 years), the mean prolactin level and the prevalence of chronic hyperprolactinemia were significantly higher in women than in men (74 vs 24 ng/mL and 93% vs 47%, respectively).[Ref]


Respiratory side effects including bronchospasm and pneumonitis have been reported rarely.[Ref]


Hematologic side effects including reversible leukopenia and leukocytosis have been reported.[Ref]


Musculoskeletal side effects including two cases of rhabdomyolysis (without evidence of overt NMS) have been reported. A case of laryngeal dystonia secondary to haloperidol (the active ingredient contained in Haldol Decanoate) has also been reported.[Ref]


Genitourinary side effects including priapism have been reported.[Ref]


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Not all side effects for Haldol Decanoate may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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